AAL2

ATM Adaptation Layer 2

ATM Adaptation Layer 2 (AAL2) is an ATM adaptation layer for Asynchronous Transfer Mode (ATM), used primarily in telecommunications; for example, it is used for the Iu interfaces in the Universal Mobile Telecommunications System, and is also used for transporting digital voice. The standard specifications related to AAL2 are ITU standards I.363.2 and I366.1.

What is AAL2?\ AAL2 is a variable bitrate, connection-oriented, low latency service originally intended to adapt voice for transmission over ATM. Like other ATM adaptation layers, AAL2 defines segmentation and reassembly of higher-layer packets into ATM cells, in this case packets of data containing voice and control information. AAL2 is further separated into two sub-layers that help with the mapping from upper layer services to ATM cells. These are named Service Specific Convergence Sub-layer (SSCS) and Common Part Sub-layer (CPS).